Winter Soldier‘s Arm is his most defining feature. It is capable of some truly crazy feats the movies will never tell you.
Can Be Detached and Controlled Remotely
It is revealed in Captain America Volume 5 that the Winter Soldier’s arms can function even after being detached from his body. The exact mechanics of that are yet to be deciphered. Either Bucky has mental implants that allow him to control his arm remotely or the arm could be pre-programmed. Either way, this means the arm could be used as a drone, getting Winter Soldier out of impossible situations. This feature is not seen in the MCU. But since Bucky has a new Vibranium arm gifted to him by Shuri, this ability could also be explored in the near future.
The metal arm is not for show. Despite being made out of lightweight titanium alloys (and later vibranium), the arm is extremely heavy. When thrown into the rear window of a car, the sheer weight of Bucky broke the window. Bucky compensates for the heavy arm with an odd stance while moving.
No Match For Actual Super Strength
Despite the bionic arm giving the Winter Soldier super human strength as an added edge, there’s still a major design flaw. The bionic arm only makes him stronger than a regular human being. It fails to put his strength in a similar class as other superheroes. In the airport hangar fight scene in Captain America: Civil War, Spider-Man caught Bucky’s arm swing single-handedly. When pit against people with true super strength, there’s not much the arm can do.
Has a Flamethrower Feature
When Bucky met another side villain called the Fixer, he made some adjustments to his arm. A flurry of new upgrades were made. One of the major upgrades was a flamethrower ability. Bucky’s Winter Soldier arm could then shoot a stream of fire as well as use jolts of electricity to hurt his foes. That would have been an epic sight to behold in the Marvel Cinematic Universe. Maybe the new Falcon and the Winter Soldier web-series will give us a first look on that feature.
Automatic Reload Functionality
When the Winter Soldier takes charge of the Thunderbolts team and attacks a SHIELD base, the Fixer gives him several upgrades to become their leader. The upgrades included a feature that allowed the arm to automatically reload any fire-arm, big or small, at his disposal. The reaction times for Bucky reduced significantly. In a firefight, the ability to reload without even giving it a second thought made him a formidable combatant.
Special Palm Print Sensors
Bucky Barnes received a lot of top notch gear during his tenure as the Winter Soldier. The bionic arm is shown to be incredible muscle definition. And they also are hinted to possess his finger prints. In Winter Soldier #4, Bucky is fighting Arkady of Project Zephyr. The latter tries to shoot him with Bucky’s gun. His hand explodes while pulling the trigger. Turns out, All of Winter Soldier’s weapons are fingerprint activated. Even his prosthetic metal arm has his finger prints.